Internal combustion engines are used to provide a source of power in motor vehicles, such as automobiles, trucks and other terrestrial vehicles. Such internal combustion engines are also used, however, in watercraft or terrestrial vehicles.
Internal combustion engines often comprise one or more cylinders, in which pistons are made to reciprocate by an explosive combustion of fuels, such as diesel or petrol fuel. The movement of one or more connecting rods resulting from combustion of the fuels is transmitted to at least one crankshaft.
In order to be able to introduce fuel into the interior of the cylinder and to carry combustion residues out of the cylinder, gas exchange valves are provided, which are capable of closing intake ports and exhaust ports in the cylinder according to the port timing. Such gas exchange valves are activated directly or indirectly. A camshaft, the cams of which act on the respective valve, is often used. The alternative or additional use of electronic components, such as piezoelectric crystals, in order to pin-point an optimum port timing remains optional. The camshaft is basically connected to the crankshaft in such a way that the movement of the crankshaft influence by means of the camshaft controls the opening or closing of the gas exchange valves.
For this purpose the system presented in EP 0 931 912 A1 provides a variable timing of the opening of the inlet and exhaust valves without changing the mechanical parts which control the displacement of the valves. Whereas in a conventional timing adjustment system the movement of each inlet or exhaust valve is clearly defined by the geometry of the mechanical parts driving the valve, in the known system described above the solenoid valve, which controls the pressurized chamber associated with a given valve, can actually be impelled to open at any time, in such a way as to drain the aforementioned chamber of pressurized oil, thereby bringing about the rapid closure of the inlet or exhaust valve under the action of the corresponding return spring means, even during a phase in which the corresponding cam would have kept the valve open.
Among other things, vertical shafts or continuous drives are used in order to establish a connection between the crankshaft and the camshaft. In modern internal combustion engines, which are used particularly in automobiles, continuous drive means, such as those used in traction drives, have gained acceptance. The means of traction used here are usually continuous drive means in the nature of a chain or a toothed belt.
Use of the traction drive to drive a further unit is also known. In this case such a unit may be an injection pump and/or a balancer shaft.
Such traction drives which are used in controlling internal combustion engines are known in the state of the art.
In older internal combustion engines a single fluid, which is also used for lubricating the traction drive and the camshaft, has hitherto been used for lubricating the crankshaft, the connecting rods and the pistons in the cylinders.
It is extremely important that the camshaft should remain synchronized with the crankshaft and that no synchronization defects should occur. This happens, for example, if the means of traction stretches, which may be attributable to increased wear. In extreme cases this even leads to complete failure of the means of traction. This problem also arises if the means of traction is embodied as a timing chain. For this reason there has been a longstanding desire to increase the service life of a means of traction, such as a timing chain.
For this purpose DE 4244052 C2, which is regarded as the generic state of the art, discloses a device for lubricating a power transmission chain in an internal combustion engine. This printed patent specification discloses the transmission of a rotational movement of a crankshaft to a camshaft by means of a chain, wherein a part of each shaft in each case extends through a crankshaft chamber or camshaft chamber containing lubricating oil and wherein the chain is enclosed by a chain case containing lubricating oil, shaft seals being intended to prevent a direct flow of lubricating oil both from the camshaft chamber and from the crankshaft chamber into the interior of the chain case, so that a lubricating oil with a low level of contamination is provided in the chain case.
Use of the very latest engines has revealed, however, that such combustion processes generate even more oil contamination in a shorter space of time, which has effects not only on the means of traction, such as timing chains, but also on the camshaft. In particular, the escape of soot particles (especially from the combustion of fuel in diesel engines), which are dissolved or flushed into the engine oil surrounding the pistons and the crankshaft, gives rise to considerable problems in the operation of conventional, modern internal combustion engines. The solution demonstrated in DE 3029964 C2 for a method of lubricating a diesel internal combustion engine also fails to solve this problem completely.